Abstract: Apparatus for detecting a load within a preselected bin of an automatic storage rack has a transducer for directing an ultrasonic beam into the bin and for detecting an echo reflected from a load struck by the beam; a digital counter adapted to generate plural bit binary pulses which is started upon initial transmission of the ultrasonic beam; and a programmable memory coupled to the counter and programmed to generate a given bin-ful output signal upon initial transmission of the beam and to subsequently generate the opposite binary bin-empty output signal if no echo has been detected when the pulses from the counter stored in the memory indicate that sufficient time has elapsed after initial transmission for the beam to travel a predetermined distance into the bin and for an echo from a load struck by the beam to return to the transducer.